Structures, Unions
How are Structures, Unions used in C++?
Explanation
Structure:
Structures in C++ is a collection of variables. Structures in C++ can be declared even without the keyword "struct". By default all the members of a structure are "public", even "private" members can also be declared in a function.
Syntax:
struct struct-type-name{
type name1: length;
type name2: length;
.
.
type nameN : length;
}variable_list;
Example :
| #include <iostream.h> struct Emp { int empno; int empsal; }; void main( ) { Emp emp1= { 23, 12000}; cout << "Employee Number::" << emp1.empno << '\n'; cout << "Employee Salary:: "<< emp1.empsal; } |
Result :
Employee Number:: 23
Employee Salary:: 12000
In the above example, the structure "Emp" is used initialize the integers, that are referenced in the "main()" function.
Unions:
Unions in C++ is a user defined data type that uses the same memory as other objects from a list of objects. At an instance it contains only a single object.
Syntax:
union union-type-name{
type member-name;
type member-name;
}union-variables;
Example :
| #include <iostream.h> union Emp { int num; double sal; }; int main() { Emp value; value.num = 2; cout << "Employee Number::" << value.num << "\nSalary is:: " << value.sal << endl; value.sal = 2000.0; cout << "Employee Number::" << value.num << "\nSalary is:: " << value.sal << endl; return 0; } |
Result :
Employee number is::2
Salary is::2.122e-314
Employee number is::0
Salary is::2000
In the above example, only "value.num" is assigned, but still the "val.sal" gets a value automatically, since the memory locations are same.
